This study presents evaluates the effectiveness of the Healthy Opportunities for Physical Activity(HOP'N) After-School Program on preventing obesity in children. The investigators hypothesized that normal and overweight/obese children attending after-school sites randomized to the control condition will increase in weight status to a greater extent compared to children at sites randomized to receive the HOP'N program. The investigators also hypothesized that after-school intervention HOP'N sites will increase in physical activity and healthful eating opportunities compared to control sites.